1. Technical Field
The present invention relates to a method for manufacturing a laminated iron core used for a motor in which permanent magnets respectively inserted into a plurality of magnet-insert holes formed so as to pass through in axial directions are sealed with a resin.
2. Background Art
Usually, as disclosed in JP-A-2010-187535, a method for manufacturing a laminated iron core is known in which a plurality of magnet-insert holes are provided in a laminated iron core body and permanent magnets are respectively inserted into the magnet-insert holes and sealed with a resin. In this manufacturing method, as shown in FIG. 3, a permanent magnet 72 is inserted into each of a plurality of magnet-insert holes 71 provided in a laminated iron core 70 and heated at a prescribed temperature. Then, each of the magnet-insert holes 71 is filled with a mold resin 75 from a lower die 73 (or an upper die 74) to harden the mold resin 75. Thus, the permanent magnet 72 is fixed to a laminated iron core body 76. FIG. 3 also shows a conveying jig 77, a lower fixing plate 78, an upper fixing plate 79, a guide post 80, and a plunger 81.
In the manufacturing method disclosed in JP-A-2010-187535, the hardened mold resin 75, namely, a resin residue remains in a resin passage part and a gate part on the surface of the laminated iron core. Accordingly, after the mold resin is injected, a process for removing the resin residue is necessary. Thus, a method for manufacturing a laminated iron core is proposed in which such a dummy plate (refer it also as to a cull plate or an intermediate plate) as described in JP-A-2011-055687 is used.
In the method for manufacturing the laminated iron core disclosed in JP-A-2011-055687, as shown in FIG. 4, a dummy plate 82 made of metal is arranged between a laminated iron core body 76 and a lower die (or an upper die), and a mold resin 75 is injected from a gate hole 83 as a resin injection opening formed in the dummy plate 82. Thus, since the injected mold resin 75 adheres to and remains on the surface of the dummy plate 82 and does not adhere to the surface of the laminated iron core body 76, the dummy plate 82 is removed from the laminated iron core body 76 to remove a resin residue at the same time. As the dummy plate is prepared so as to meet the kind of the laminated iron core body, a plurality of kinds of laminated iron core bodies may be advantageously sealed with a resin in one molding die. FIG. 4 also shows a runner 84 (a resin passage) formed in the dummy plate 82.